Calipers



UNITED STATES "PATENT OFFICE.

LESLIE B. WOODRUFF, OEMOHIOAGO, ASSIGNOE To IIIMSELE, AND JAMES SHAW AND ALBERT J. HOPKINS, OE AURORA, ILLINOIS.

CAMPERS.

To all 'whom tt mag/concern:

Be it known that I, LESLIE B. WOODRUFF', a citizen ofthe United States, residing at Ohicago, in the county of (look and State ofllli-V The invention consists in providing the in` zo strument, which is one having its two parts freely'adj ustable on a xed pivotnvilh two sets of legs or measuiingpoints, one ot' which sets being adjusted to indicate thedia-Ineter of any object, the other will at the same time be ad.-

just-ed to indicate the circumference corresponding thereto, and vice versa. 4 i

In the following description the term leg7 will be used to indicate the whole piece of metal from the point ato the point a,or from 3o` the point a3 to the point a., as the case may be.

In the drawings, A A' represent a pai-r ot' dividers pointed at each end a a a2 a3, said four points, a ct' a2 a3, beingV as nearly as possible inV the horizontal plane in which the adjacent surfaces of said legs A A lie, and having their legs fastened in a suitable manner with a pivot, b, the center line, b b2, of which passes vertically through the point B, which point B is insaid horizontal plane and at the 4o intersection ofthe vertical planes through the dotted lines terminating respectivelyinpoints a2 a and a3 et. y

On each of the legs A A', respectively, are placed the pointed knobs C GV ,ha;ngrespeot ively points c c'. The points c c are in therespective vertical planes ot the respectivedotf ted lines, which terminate respectively in the points a2 a. and a3 a. The Lipper leg, A', is provided with a slot7 SPECIFICATION forming part of Letters Patent No. 252,410, dated January 17, 18.52.

A Application filedp May 1S, `1881. (No model.)A i

c2, of such shape and position-tl1at said legA 5o in closing over the. leg'Alwill not be interfered with by the knob C, the two pointed knobs C C being at such distance from the vertical y line b b2,through point'B, and in such posi. tion in relation to thei'l1 respective legs that 55 when the dividers arethus closed said knobs Will together have in plan view theappearance of a single knob, and their points will be practically .equidistant from the said vertical line through point B. l Thedistance between the points a. a always bears the Same proportion to the distance between `the points a2 a3 whatever maybe the an# gular adjustment of the dividers. Diameters and circumfcrences increase and decrease in direct proportion to each other, andr in myinvention the points t a are equidistant from point B, and at any given adjustment of the legs A A in their relation to each other are at such a distance from each other that the ratio 7o ot' this distance to the distance between points a2 a3 which are also equidistant from point B) is equal to the ratio of a diameter 'to its circumterence. Moreover, at any given angular adi justinent of said legs A A therat'io ofthe djs- 7 5 tance between points c c (which are equidistantfromfsaid vertical line throughV point B and in a plane parallel to said horizontal plane) to the distance between the points u? a3 equals the ratio ot' a diameter to its circumference. Sc When the pontscc, respectively,are set on the ends ol a diameter, the points a2 a3 are thereby set at a distance from each other equal lo the lengthofthecorrespondingcircumference,and, r vice versa, when the points a2 a3, respectively, 85 are set on the ends ot a line representing the length of a circumference, the points c c will thereby beset at a distance. from eachother equal to the length of the corresponding diameter, the object ot' the points c c being the 9o i saine as that ot' points a a.

The foregoing description is equally applicable to calipers or other similar instruments.

Obviously partsi of this apparatus `may be changed in details of construction without departing from the main principle ot' constructionby means of whichthe operation above described issecured, this principle being that .ratio between a diameter and its circumference, the points c c being merely offsets lfrom points Whieh are perpendicularly below them and which come within the statement of principle just given. I do not wish to be understood, therefore, as limiting my invention to theapparatus in all its details as herein shown and described. For example, although thel pointed knobs C C and their accompanying slot have been shown only in one figure, of course these or their equivalents may be sup'- plied, when desired, in other forms of instru- ,ments embodying my invention; and as tothe pair of knobs C C and the pair of points a a',

' either one of the pairs may be omitted from any instrument provided it has the other pair or their equivalents. Again, the points with which measurements are taken or transferred need not necessarily be of the exact description shown and above described; but scalemarks or other suitable devices may of course answer the same purpose. Y

A Wing and set-sere7 for the purpose of securing the legs at any desired adjustment, or scales for indicating the distance apart of the points, may be used when desired.

Having thus described my invention, what I claim as new," and desire to secure by Letters latent, is-

1. Compasses, calipers, or other similar instruments freely adjustable on a fixed pivot, on each leg of which instrument are indicated, in

any suitable manner, (including offsets,) distances from the point B,'the ratio between which distauees on a given leg is equal to the ratio between a diameter and its circumference, substantially as and for the purpose described.

2. Compasses, calipers, or other similar instruments vfreely adjustable on a flXed pivot, and provided with two sets of'points, a a and a2 a3, arranged and operating substantially as and for the purposes set forth.

3. Compasses, calipers, or other similar instruments freely adjustable on a fixed pivot,

and provided with two sets of points, c o and 5o a2 a3, located on the same side of the pivot and arranged and operating substantially as and for the purposes set forth.

LESLIE B. WOODRUFF.

Witnesses i fGio. R. CUTLER,

THOMAS H. PnAsn, 

